docs: def parse_track_header(self, fp):
          """Return the size of the track chunk."""
          # Check the header
          try:
              h = fp.read(4)
              self.bytes_read += 4
          except:
              raise IOError("Couldn't read track header from file. Byte %d."
                      % self.bytes_read)
          if h != 'MTrk':
              raise HeaderError('Not a valid Track header. Byte %d.'
                      % self.bytes_read)
  
          # Parse the size of the header
          try:
              chunk_size = fp.read(4)
              self.bytes_read += 4
          except:
              raise IOError("Couldn't read track chunk size from file.")
          chunk_size = self.bytes_to_int(chunk_size)
          return chunk_size